United States Patent [19]
`Norton et al.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,943,491
`Jul. 24, 1990
`
`[54] STRUCTURE FOR IMPROVING
`INTERCONNECT RELIABILITY OF FOCAL
`PLANE ARRAYS
`
`[75]
`
`[73]
`[21]
`[22]
`[51]
`[52]
`
`[53]
`
`[56]
`
`Inventors: Peter W. Norton, Littleton; James A.
`Stobie, Westford; Peter H.
`Zimmermann, Lexington, all of Mass.
`Assignee: Honeywell Inc., Minneapolis, Minn.
`Appl. No.: 438,241
`Filed:
`Nov. 20, 1989
`
`Int. Cl.5 ....................... .. H01L 27/14; GOlJ l/OO
`US. Cl. .................................. .. 428/620; 250/332;
`250/338.4; 250/370.08
`Field of Search ............. .. 428/620, 641, 674, 642,
`428/616, 624, 618, 626; 250/332, 349, 370.08,
`338.4
`
`V References Cited
`U.S. PATENT DOCUMENTS
`
`3,808,435 4/ 1974 Bale et a1. ......................... .. 250/332
`4,039,833 8/ 1977
`4,064,533 12/1977
`4,067,104 l/l978
`4,228,365 10/1980
`4,379,232 4/1983
`4,536,658 8/1985
`4,740,700 4/ 1988 Shuham et a1. ................... .. 250/344
`
`. . . .. 250/211 R
`
`Schmitz . . . . . . . . . .
`
`4,757,210 7/1988 181131818181. ................... .. 357/30H
`4,783,584 11/1988 Schulte at al. .
`250/37008
`4,792,672 12/1988
`4,868,902 9/1989
`Sato ....................................... .. 330/9
`Primary Examiner-John J. Zimmerman
`Attorney, Agent, or Firm—Haugen and Nikolai
`[57]
`ABSTRACT
`An improved structure for interconnecting focal plane
`arrays. A ?rst body having a ?rst coefficient of expan
`sion comprising a detector array is connected by inter
`connection apparatus to a second body having a second
`coefficient of expansion. The second body comprises
`semiconductor electronics and includes a bottom sur
`face which opposes the surface connected to the ?rst
`body. A layer of material is bonded with an adhesive to
`the second body’s bottom surface wherein the bonded
`layer has a third coef?cient of expansion which is
`greater than the ?rst and second coef?cients of expan
`sion. In one aspect of the invention, the interconnection
`apparatus comprises interconnect columns made sub
`stantially of indium, the second body is substantially
`comprised of silicon and the ?rst body is substantially
`comprised of material selected from the group consist
`ing of CdTe and HgCdTe. The bonded layer may ad
`vantageously be substantially comprised of copper.
`
`19 Claims, 1 Drawing Sheet
`
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`FOCAL PLANE ARRAY
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`MULTIPLEXER
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`32
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`/]
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`0
`
`Raytheon2058-0001
`
`Sony Corp. v. Raytheon Co.
`
`
`IPR2015-01201
`
`

`

`US. Patent
`
`Jul. 24, 1990
`
`4,943,491
`
`20
`
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`Raytheon2058-0002
`
`
`IPR2015-01201
`
`

`

`1
`
`4,943,491
`
`STRUCTURE FOR IlVIPROVING INTERCONNECT
`RELIABILITY OF FOCAL PLANE ARRAYS
`
`BACKGROUND OF THE INVENTION
`This invention is directed generally to apparatus for
`electrically interconnecting electrical elements, and,
`more particularly, to an improved structure for use in
`connecting focal plane array components to each other
`as used in electromagnetic sensing devices, such as in
`frared sensing devices.
`
`5
`
`20
`
`2
`SUMMARY OF THE INVENTION
`The invention provides an improved structure for
`interconnecting focal plane arrays. A ?rst body having
`a ?rst coef?cient of expansion comprising a detector
`array is connected by interconnection means to a sec
`ond body having a second coef?cient of expansion. The
`second body comprises semiconductor electronics and
`includes a bottom surface which opposes the surface
`connected to the ?rst body. A layer of material is
`bonded with an adhesive to the second body’s bottom
`surface wherein the bonded layer has a third coef?cient
`of expansion which is greater than the ?rst and second
`coef?cients of expansion. Alternatively, the second
`body is grown epitaxially on the third body, in which
`case no adhesive is required.
`In one aspect of the invention, the interconnection
`means comprises interconnect columns made substan
`tially of indium, the second body is comprised of mate~
`rial selected from the group consisting of silicon and
`sapphire and the ?rst body is substantially comprised of
`material selected from the group consisting of CdTe
`and HgCdTe.
`,
`It is one object of the invention to provide an im
`proved structure for interconnecting focal plane arrays
`wherein the reliability of the indium column intercon
`nects are improved by forcing a silicon multiplexer
`assembly to follow thermal expansion and contraction
`of the detector array assembly by laminating highly
`thermal expansive material to the silicon multiplexer
`electronics.
`It is yet another object of the invention to reduce
`mechanical stress on indium interconnects used in man
`ufacturing focal plane arrays between the detector
`array and the multiplexer, thereby improving the reli
`ability of the indium interconnects.
`Other objects, features and advantages of the inven
`tion will be recognized by those skilled in the art
`through the description of the preferred embodiment,
`claims, and drawings herein, wherein like numerals
`refer to like elements.
`
`DISCUSSION OF THE PRIOR ART
`Bump bonding has been used for a number of years
`for joining infrared detector array pixels to associated
`electronics such as multiplexer circuits. Such intercon
`nection bumps provide both electrical, thermal and
`mechanical interconnects in hybrid Focal Plane Arrays
`(FPAs) at room temperature as well as at cryogenic
`temperatures. The detector pixels are typically com
`prised of material sensitive to receiving electromagnetic
`radiation, such as infrared radiation. Materials com
`monly employed are mercury cadmium telluride
`(HgCdTe) and cadmium telluride (CdTe). The associ
`ated multiplexer electronics are usually embedded in
`CMOS packaging comprised typically of silicon (Si).
`FPAs usually employ solid metal bumps as, for exam
`ple, indium bumps for achieving a cold weld intercon
`nection between the multiplexer electronics and the
`infrared detector pixels. Examples of such focal planes
`include PV HgCdTe-Si, PV InSb-Si, PtSi-Si, and ex
`trinsic Si-Si focal planes. Prior art con?gurations typi
`cally use opposing bumps of the same shape, material
`35
`and cross-section. For optimum bump-bonding integ
`rity, the opposing bumps are aligned for maximum
`overlap.
`The manufacturing of focal plane arrays requires
`bonding focal plane arrays made of CdTe or HgCdTe
`to associated electronics such as multiplexer electronics.
`The focal plane arrays are typically manufactured in
`room temperature environments. However, such arrays
`are typically operated under cryogenic temperatures.
`As a result, the reliability of the current interconnect
`technology is less than optimum because the metal col
`umn interconnects take all of the stress induced by dif
`ferences in thermal expansion and contraction which
`exist between the detector array and the readout multi
`plexer electronics. Speci?cally, the detector array being
`comprised of a compound semiconductor will have a
`higher coef?cient of expansion than the readout multi
`plexer which is usually comprised of a semiconductor
`material such as silicon.
`The present invention overcomes the perceived dis
`advantages of the prior art by laminating a layer of
`material having a high coef?cient of expansion to the
`body bearing the readout electronics. The laminated
`material has thermal expansion and contraction proper
`ties selected to force the semiconductor material to
`follow and match the expansion and contraction of the
`detector array. In this way, the semiconductor substrate
`is forced to follow the detector array thermal expansion
`and contraction, thus reducing stress on the intercon
`nect columns. Since the mechanical stress on the inter
`connects between the detector array and the semicon
`ductor body is reduced, the reliability of the metallic
`interconnects is improved.
`
`45
`
`60
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The sole FIGURE schematically illustrates one em
`bodiment of the structure of the invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`Referring now to the sole FIGURE, the improved
`interconnection structure of the invention is illustrated.
`Those skilled in the art will appreciate that the embodi
`ment shown in the FIGURE is intended to highlight the
`principal features of the invention and is not intended to
`so limit the invention. The interconnection structure
`includes a ?rst body 10, a second body 30, means for
`interconnecting the ?rst and second bodies 20, an adhe
`sive layer 40, and a third body layer 50, having a large
`expansion coef?cient. The ?rst body typically com
`prises a focal plane array which is made from materials
`substantially comprised of CdTe, HgCdTe or other
`materials used for radiation detection. The interconnect
`columns 20 are mounted by conventional means to the
`focal plane array in order to provide interconnections
`to associated electronics located on the second body 30.
`The interconnect columns are typically made substan
`tially of indium. The second body is typically silicon but
`may also be comprised substantially of other semicon
`
`Raytheon2058-0003
`
`
`IPR2015-01201
`
`

`

`15
`
`30
`
`4,943,491
`3
`4
`ductor materials as are typically used in manufacturing
`7. The structure of claim 1 wherein the bonded layer
`large scale or very large scale integrated circuits.
`is substantially comprised of Cu.
`Layer 50 is advantageously comprised of copper or a
`8. The structure of claim 1 wherein the second body
`comprises a readout multiplexer.
`similar material and may be bonded to the bottom sur
`9. The structure of claim 8 wherein the second body
`face of the second body 30 by means of an adhesive
`is substantially comprised of Si.
`layer 40 according to bonding techniques well known in
`10. The structure of claim 1 wherein the interconnec
`the art. Adhesive layer 40 may be any well-known ad
`tion means comprises a plurality of metal column inter
`hesive Epotek Brand epoxy or glue. Layer 50 is selected
`connects.
`to have a coef?cient of expansion which is greater than
`11. The structure of claim 10 wherein the metal col
`both the coefficients of expansion for the ?rst and sec
`umn interconnects are substantially comprised of in
`ond bodies. Typically, the material chosen as layer 50
`dium.
`will advantageously have a coef?cient of expansion at
`12. An improved structure for interconnecting infra
`least twice as great as the coef?cient of expansion of
`red focal plane arrays comprising:
`silicon as the case may be.
`(a) a ?rst body having a first coef?cient of expansion
`In another aspect of the invention, the second body
`including a detector array which is substantially
`may be epitaxially grown or otherwise deposited on the
`comprised of material selected from the group
`third body. In such cases, it is not necessary to employ
`consisting of CdTe and HgCdTe;
`an adhesive to join the second body to the third body.
`(b) a second body having a second coef?cient of
`This invention has been described herein in consider
`expansion including multiplexer electronics sub
`able detail in order to comply with the Patent Statutes
`stantially comprised of material selected from the
`and to provide those skilled in the art with the informa
`group consisting of Si and sapphire, wherein the
`tion needed to apply the novel principles and to con
`second body includes a bottom surface;
`struct and use such specialized components as are re
`(0) a plurality of indium column interconnects
`quired. However, it is to be understood that the inven
`wherein the interconnects bond the ?rst and sec
`tion can be carried out by speci?cally different equip- '
`ond bodies; and
`ment and devices, and that various modi?cations, both
`(d) a layer bonded with adhesive to the second body’s
`as to the equipment details and operating procedures,
`bottom surface, and wherein the layer has a third
`can be accomplished without departing from the scope
`coef?cient of thermal expansion at least twice as
`of the invention itself.
`great as the ?rst and second coefficients of expan
`What is claimed is:
`sion.
`13. An improved structure for interconnecting focal
`1. An improved structure for interconnecting focal
`plane arrays comprising:
`plane arrays comprising:
`(a) a ?rst body having a ?rst coef?cient of thermal
`(a) a ?rst body having a ?rst coef?cient of thermal
`expansion including a detector array;
`35
`expansion comprising a detector array;
`(b) a second body having a second coef?cient of
`(b) a second body having a second coef?cient of
`expansion substantially equal to the ?rst coef?cient
`thermal expansion comprising semiconductor elec
`of expansion;
`tronics having a bottom surface;
`(c) a third body which is epitaxially grown on the
`(0) means for interconnecting the ?rst and second
`second body and whereon multiplexer electronics
`bodies; and
`are fabricated; and
`(d) a layer of material bonded with adhesive to the
`(d) means for interconnecting the multiplexer elec
`second body’s bottom surface wherein the bonded
`tronics and the detector array.
`layer has a third coef?cient of thermal expansion
`14. The structure of claim 13 wherein the ?rst body is
`greater than the ?rst and second coef?cients of
`substantially comprised of material selected from the
`45
`thermal expansion.
`group consisting of CdTe and HgCdTe.
`2. The structure of claim 1 wherein the ?rst body is
`15. The structure of claim 14 wherein the third body
`substantially comprised of material selected from the
`is substantially comprised of Si.
`group consisting of CdTe and HgCdTe.
`16. The structure of claim 15 wherein the second
`3. The structure of claim 2 wherein the second body
`body is an alloyed metal.
`is substantially comprised of Si.
`17. The structure of claim 16 wherein the second
`4. The structure of claim 3 wherein the bonded layer
`body is substantially comprised of Cu.
`is an alloyed metal.
`18. The structure of claim 13 wherein the second
`5. The structure of claim 4 wherein the bonded layer
`body is an alloyed metal.
`is substantially comprised of Cu.
`'
`19. The structure of claim 13 wherein the second
`6. The structure of claim 1 wherein the bonded layer
`body is substantially comprised of Cu.
`is an alloyed metal.
`1!
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`It
`*
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`40
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`55
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`65
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`Raytheon2058-0004
`
`
`IPR2015-01201
`
`